Weakened virus makes better vaccine

Rewriting the genetic code of the flu virus has helped to produce a stronger immune response, studies on mice have shown.

The new vaccine contains exactly the same proteins as the flu virus it targets but the sequence code has been changed. A team of researchers found that by altering certain DNA sequences the virus replicated more slowly, allowing for a more efficient immune response.

Scientists exploited this replication weakness after noticing that some of the three letter DNA sequences, known as codons, are favoured for replication over others by the virus. Usually the sequences chosen by the virus are the ones that translate the code into proteins most efficiently. By changing the codons, the team made the virus replicate slowly.

Mice that were given the vaccine remained healthy. After four weeks they were infected with a potentially fatal strain of flu which had little or no effect; three days later, the virus was undetectable in four fifths of mice. The researchers hope their vaccine will be especially useful when dealing with seasonal or pandemic flu strains.